The invention relates to a method for monitoring the wheels of a motor vehicle for fault states, in particular for incorrect tire pressures, in which each wheel to be monitored is assigned a wheel unit which transmits data to a central evaluation device of the vehicle at least in response to a trigger signal, the occurrence of a fault state and the wheel position of the wheel at which the fault state has occurred being indicated. In addition, the invention relates to a system for monitoring the wheels of a motor vehicle for fault states, in particular for incorrect tire pressures, having a plurality of wheel units and having a central evaluation device, each wheel to be monitored being assigned a wheel unit which transmits data to a central evaluation device of the vehicle at least in response to a trigger signal, and the occurrence of a fault state and the wheel position of the wheel at which the fault state has occurred being indicated.
The term fault state is to be interpreted loosely in the present context and comprises all states which are considered to be worthy of detection.
With respect to the methods of the generic type and the systems of the generic type it is known, for example, that the wheel units transmit information to a central evaluation device, arranged on the chassis of the motor vehicle, by means of radio frequency signals. In the present context, wheel units are to be understood as any unit which rotates with a respective wheel and is suitable for supplying information or data by means of which fault states which possibly occur at the wheel can be detected. In addition to the actual detection of a fault state, it is necessary to determine at least the wheel position (for example front left, front right, rear left, rear right) of a wheel at which a fault state has occurred. For this purpose, in the known methods and systems the wheel position of all the wheels is detected and stored so that, for example, a central evaluation device already knows which data transmitted for detecting a fault state is assigned to which wheel position. For example, EP 0 806 307 B1 has already disclosed a method for carrying out the assignment of the wheel position to air pressure monitoring devices in an air pressure monitoring system of a motor vehicle, the motor vehicle having, inter alia, the following components: a number of wheels, each wheel being assigned an air pressure monitoring device which is capable of transmitting an individual identifier to a central processor unit, and a central processor unit in which the assignment of the identifier to an air pressure monitoring device relating to the wheel position for each wheel is stored. In the method known from EP 0 806 307 B1, the assignment of the air pressure monitoring device to the wheel position is performed as follows: an assignment mode is switched on; the individual identifiers of the air pressure monitoring device are output; the central processor unit evaluates which individual identifier has been transmitted from which wheel position; the assignment which is detected in the central processor unit is stored; and the assignment mode is switched off and the air pressure monitoring system is operated in a pressure monitoring mode. In order to evaluate the individual identifiers, there is, in particular, provision here for a specific variable, for example the wheel speed, for each wheel of the motor vehicle to be measured both with a wheel unit of the air pressure monitoring device and with a fixed sensor with a known wheel position. Then, the wheel position of the individual wheels is determined by comparing the output signals of the fixed sensors and the output signals of the wheel units. DE 197 20 123 C2 also discloses that a separate antenna is to be provided in the region of each wheel to be monitored, which antenna can be used to receive signals emitted by the wheel units. Although each of the antennas can, under certain circumstances, also receive signals from wheel units which are not arranged directly adjacent to the respective antenna, according to the teaching of DE 197 20 123 C2 it is sufficient, for determining the wheel position of the individual wheels, to assume that a signal which is emitted and received by a directly adjacent wheel unit has a higher signal level than a signal which is received by a more remotely arranged wheel unit. The known systems and methods have in common the fact that they are very complex and therefore expensive in terms of the hardware and software necessary to determine the wheel positions.
The invention is based on the object of developing the methods of the generic type and the systems of the generic type in such a way that at least the wheel position of a wheel at which a fault state has occurred can be determined with a relatively small amount of expenditure on hardware and software.
This object is achieved by a method for monitoring the wheels of a motor vehicle for fault states, in which each wheel to be monitored is assigned a wheel unit which transmits data to a central evaluation device of the vehicle at least in response to a trigger signal, the occurrence of a fault state and the wheel position of the wheel at which the fault state has occurred being indicated, the detection and the indication of the wheel position of the wheel at which the fault state has occurred being triggered after the fault state has been indicated, wherein the wheel position of the wheel at which the fault state has occurred is detected without all the wheel positions being stored, and said detection comprises a further trigger signal being supplied to at least one wheel unit at a known wheel position.
The detection of the wheel position of the wheel at which the fault state has occurred can be triggered manually. The further trigger signal can be supplied to the at least one wheel unit at the known wheel position by the valve of the corresponding wheel being touched. The further trigger signal can be supplied to the at least one wheel unit at the known wheel position by a portable transmitter being activated in the vicinity of the corresponding wheel. The portable transmitter may be formed by the remote control of a vehicle locking system. The further trigger signal may further be supplied to the at least one wheel unit at the known wheel position by a magnet being moved into the vicinity of the corresponding wheel. The further trigger signal may be supplied to the at least one wheel unit at the known wheel position by an inductive field being generated in the vicinity of the corresponding wheel. The wheel unit can transmit further data to the central evaluation device in response to the further trigger signal, in that the central evaluation device compares the further data with stored data in order to determine whether the further data originates from the wheel unit which is assigned to the wheel at which the fault state has occurred, and in that the wheel position is indicated if it is determined that the further data originates from the wheel unit which is assigned to the wheel at which the fault state has occurred. Each wheel unit may store when it transmits to the central evaluation device data which allows a fault state to be determined, and in that the at least one wheel unit triggers, at a known wheel position, the indication of the wheel position in response to the further trigger signal if it has transmitted to the central evaluation device data which allows a fault state to be determined. The wheel position can be indicated by generating an audible and/or a visual signal. The wheel position can also be indicated by actuating one or more indicator lights and/or one or more headlights and/or one or more tail lights and/or the horn of the motor vehicle. The data, and if appropriate the further data, can be transmitted to the central evaluation device from the wheel units via a radio link. The fault state can be a state for incorrect tire pressures.
An embodiment of the present invention ca be a system for monitoring the wheels of a motor vehicle for fault states having a plurality of wheel units and having a central evaluation device, each wheel to be monitored being assigned a wheel unit which transmits data to a central evaluation device of the vehicle at least in response to a trigger signal, the occurrence of a fault state and the wheel position of the wheel at which the fault state has occurred being indicated, and the detection and the indication of the wheel position of the wheel at which the fault state has occurred being triggered after the fault state has been indicated, wherein it has trigger means which, when activated, cause a further trigger signal to be supplied to at least one wheel at a known wheel position in order to detect, without storing all the wheel positions, the wheel position of the wheel at which the fault state has occurred.
The system can have activation means by means of which the detection of the wheel position of the wheel at which the fault state has occurred can be triggered manually. The trigger means can be formed in the region of a valve of a corresponding wheel, and in that the trigger means are activated by touch. The trigger means may also be formed by a portable transmitter which is activated in the vicinity of the corresponding wheel in order to supply the further trigger signal. The portable transmitter can be formed by a remote control of a vehicle locking system. The trigger means may be formed by a magnet which, having been moved into the vicinity of the corresponding wheel supplies of the further trigger signal. The trigger means can generate an inductive field in order to supply the further trigger signal. The wheel unit can transmit further data to the central evaluation device in response to the further trigger signal, in that the central evaluation device compares the further data with stored data in order to determine whether the further data originates from the wheel unit which is assigned to the wheel at which the fault state has occurred, and in that it indicates the wheel position if it is determined that the further data originates from the wheel unit which is assigned to the wheel at which the fault state has occurred. Each wheel unit may store when it transmits to the central evaluation device data which allows a fault state to be determined, and in that the at least one wheel unit triggers, at a known wheel position, the indication of the wheel position in response to the further trigger signal if it has transmitted to the central evaluation device data which allows a fault state to be determined. The system may have audible and/or visual signaling means for indicating the wheel position. The signaling means can comprise one or more indicator lights and/or one or more headlights and/or one or more tail lights and/or the horn of the motor vehicle. The data, and if appropriate the further data, can be transmitted to the central evaluation device from the wheel units via a radio link. The fault state can be a state for incorrect tire pressures.
The method according to the invention is based on the prior art of the generic type in that the detection and the indication of the wheel position of the wheel at which the wheel state has occurred is triggered after the fault state has been indicated. As a result of this solution, the wheel position of a wheel has to be determined only very rarely, specifically only after a fault state has occurred. In the method explained at the beginning, it is, in contrast, always necessary for the wheel position of all the wheels to be determined if in the meantime a wheel change was possible. As a result of the solution according to the invention, it is also no longer necessary to store the wheel positions of all the wheels.
In one particularly preferred development of the method according to the invention there is provision for the detection of the wheel position of the wheel at which the fault state has occurred to be triggered manually. Here, in particular embodiments are considered in which the detection of the wheel position of the wheel at which the fault state has occurred is triggered manually only if the vehicle has stopped, that is to say at a time at which there is no longer pronounced danger.
In particular in the context explained above, the method according to the invention can also provide for the detection of the wheel position of the wheel at which the fault state has occurred to comprise a further trigger signal being supplied to at least one wheel unit at a known wheel position.
For this purpose, the method according to the invention can provide for the further trigger signal to be supplied to the at least one wheel unit at the known wheel position by the valve of the corresponding wheel being touched. The touching of the valve can be detected here by means of impedance measurements, for example.
The method according to the invention can alternatively provide for the further trigger signal to be supplied to the at least one wheel unit at the known wheel position by a portable transmitter being activated in the vicinity of the corresponding wheel. The two solutions explained above have in common the fact that a further trigger signal can be supplied in succession to a wheel unit until the wheel or the wheel position at which the fault state has occurred is detected.
If a portable transmitter is used to generate the further trigger signal, the method according to the invention provides, in an advantageous refinement, for the portable transmitter to be formed by the remote control of a vehicle locking system. Here, the further trigger signal can correspond to the signal provided on a standard basis by the remote control of the motor vehicle locking system, or the remote control can have additional pushbutton keys which are provided specifically for generating the further trigger signal.
As an alternative to touching the wheels or using a portable transmitter, the method according to the invention can provide for the further trigger signal to be supplied to the at least one wheel unit at the known wheel position by a magnet being moved into the vicinity of the corresponding wheel. Such a magnet can be both a permanent magnet and a electromagnet.
Alternatively, the method according to the invention can also provide for the further trigger signal to be supplied to the at least one wheel unit at the known wheel position by an inductive field being generated in the vicinity of the corresponding wheel. In specific embodiments it can be generally advantageous if the further trigger signal is generated in the same way or similar way to a trigger signal which is transmitted, for example, to the wheel unit from a central evaluation device in order to request data.
In particularly preferred embodiments of the method according to the invention there is provision for the wheel unit to transmit further data to the central evaluation device in response to the further trigger signal, for the central evaluation device to compare the further data with stored data in order to determine whether the further data originates from the wheel unit which is assigned to the wheel at which the fault state has occurred, and for the wheel position to be indicated if it is determined that the further data originates from the wheel unit which is assigned to the wheel at which the fault state has occurred. The further data here can, in particular, comprise identifiers which are uniquely assigned to the respective wheel units. In this case, the stored data also comprises the respective identifiers of the wheel units.
The method according to the invention can advantageously also provide for each wheel unit to store when it transmits to the central evaluation device data which allows a fault state to be determined, and for the at least one wheel unit to trigger, at a known wheel position, the indication of the wheel position in response to the further trigger signal if it has transmitted to the central evaluation device data which allows a fault state to be determined. With this solution, it is in particular possible to dispense with specific identifiers of the wheel units so that identical wheel units can be used for all the wheels. However, said wheel units are preferably successively requested to transmit data.
The method according to the invention also preferably provides for the wheel position to be indicated by generating an audible and/or a visual signal. In this context, in particular binary, audible and/or visual signals are preferred.
In this context, the method according to the invention can, for example, provide for the wheel position to be indicated by actuating one or more indicator lights and/or one or more headlights and/or one or more tail lights and/or the horn of the motor vehicle.
In all the embodiments of the method according to the invention it is preferably provided that the data, and if appropriate the further data, is transmitted to the central evaluation device from the wheel units via a radio link. In particular, radio-frequency radio links are considered here.
Any system which is suitable for carrying out an embodiment of the method according to the invention falls within the scope of protection of the respective claims.
The system according to the invention is based on the generic prior art by virtue of the fact that it triggers the detection and the indication of the wheel position of the wheel at which the fault state has occurred after the fault state has been indicated. As a result, the advantages explained in conjunction with the method according to the invention are obtained in the same or in a similar way, for which reason reference is made to the corresponding explanations in order to avoid repetitions.
The same applies analagously to the following preferred embodiments of the system according to the invention, reference also being made to the corresponding explanations of the advantages which can be achieved by these embodiments in conjunction with the method according to the invention.
With advantageous embodiments of the system according to the invention there is also provision for it to have activation means by means of which the detection of the wheel position of the wheel at which the fault state has occurred can be triggered manually.
Furthermore, embodiments of the system according to the invention are considered advantageous in which there is provision for it to have trigger means which, when activated, cause a further trigger signal to be supplied to at least one wheel unit at a known wheel position in order to detect the wheel position of the wheel at which the fault state has occurred.
In this context it is also possible to provide for the trigger means to be formed in the region of a valve of a corresponding wheel, and for the trigger means to be activated by touch.
Alternatively, with the system according to the invention there can be provision for the trigger means to be formed by a portable transmitter which is activated in the vicinity of the corresponding wheel in order to supply the further trigger signal.
In this case it is preferred for the portable transmitter to be formed by the remote control of a vehicle locking system.
However, it is also possible to consider embodiments of the system according to the invention in which there is provision for the trigger means to be formed by a magnet which, having been moved into the vicinity of the corresponding wheel, supplies the further trigger signal.
Furthermore, the present invention comprises systems in which there is provision for the trigger means to generate an inductive field in order to supply the further trigger signal.
Similarly to the method according to the invention, particularly preferred embodiments of the system according to the invention also provide for the wheel unit to transmit further data to the central evaluation device in response to the further trigger signal, for the central evaluation device to compare the further data with stored data in order to determine whether the further data originates from the wheel unit which is assigned to the wheel at which the fault state has occurred, and for it to indicate the wheel position if it is determined that the further data originates from the wheel unit which is assigned to the wheel at which the fault state has occurred.
Furthermore, in the system according to the invention there can be provision for each wheel unit to store when it transmits to the central evaluation device data which allows a fault state to be determined, and for the at least one wheel unit to trigger, at a known wheel position, the indication of the wheel position in response to the further trigger signal if it has transmitted to the central evaluation device data which allows a fault state to be determined.
In preferred embodiments of the system according to the invention there is provision for it to have audible and/or visual signaling means for indicating the wheel position.
Here, there may be provision, for example, for the signaling means to comprise one or more indicator lights and/or one or more headlights and/or one or more tail lights and/or the horn of the motor vehicle.
Similarly to the method according to the invention, with the system according to the invention there is preferably provision for the data, and if appropriate the further data, to be transmitted to the central evaluation device from the wheel unit via a radio link.
The invention is based on the recognition that the necessary expenditure on hardware and software and/or the necessary computing time can be significantly reduced if at least the wheel position at which a fault state has occurred is determined only after the occurrence of a fault state.